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25 April 2021 6 min read

The Great Barrier Reef (GBR) is the world’s largest coral reef ecosystem. It stretches 2300 km from the Gulf of Papua to the New South Wales border, comprises over 3500 individual reefs, is World Heritage listed, contributes over $6.4B annually to the Australian economy and supports more than 64,000 jobs. It is also facing an unprecedented number of hard-to-predict threats, including climate change, reduced water quality, crown-of-thorns starfish outbreaks, ocean acidification, and port development and shipping. Needless to say, managing such a large, complex, valuable and threatened ecosystem is no simple task.

Providing integrated information to inform management decisions

eReefs aims to make this important task more manageable by providing integrated environmental information about the GBR to all its stakeholders. eReefs has been developed through a collaboration between the Great Barrier Reef Foundation, CSIRO, the Australian Institute of Marine Science, Bureau of Meteorology, and Queensland Government. It is a freely-accessible online platform that provides a picture of what is currently happening on the reef and what will likely happen in the future under specified scenarios. It allows users to explore the impact of possible management options for mitigating threats to the GBR, including assessing outcomes for the multiple and sometimes competing uses of the reef.

eReefs integrates data, catchment and nested marine models, visualisation, reporting and decision support tools. It delivers a range of products including real-time model predictions for the entire GBR, aggregated and regionalised model outputs, and satellite-derived water quality and reef temperature and coral bleaching information. In other words, eReefs draws on a wide range of data from various sources and enables users to explore this data in different ways depending on their needs.

As Dr Andy Steven, leader of CSIRO’s Blue Growth Strategy and Impact Portfolio, explains, a team of more than 40 scientists from wide ranging disciplines worked with key GBR stakeholders on a regular basis to ensure that eReefs met the many and varied needs of its intended users.

“I think one of the keys to the success of eReefs has been the ongoing engagement between the development team and representatives from eReefs’ end-user groups including government agencies, regional natural resource management groups, industries such as tourism, shipping and ports, researchers and the general public,” said Dr Steven.

“Over the six years we spent developing eReefs, it was rewarding to see this engagement move from initial scepticism and distrust, particularly when it came to models and remote sensing, to positive endorsement and adoption of the platform.”

Science-backed water quality improvement targets

eReefs has become an essential tool in the Australian and Queensland governments’ efforts to protect and preserve the GBR. The products within eReefs have been used to inform operational activities, enable reporting of marine water quality and for scenario planning to address a number of issues confronting the GBR.

One such issue is the impact agricultural activities have on water quality on the GBR. Agriculture in the GBR catchments has been shown to increase the amount of pollutants, such as nutrients and sediment, in waters running off the land, into rivers and out into the GBR lagoon. The amount of pollutants in the water coming from a particular catchment area is called the catchment load. If too much or the wrong ratios of these pollutants end up in the lagoon, they can negatively impact reef ecosystems.

As this satellite image shows, pollutants, such as sediment, flow from the catchment on to the reef, where they can reduce water quality and negatively impacting reef ecosystems.

As Dr Mark Baird, leader of CSIRO’s Coastal Biogeochemical Modelling team explains, eReefs enabled his team to quantify the water quality benefits gained from reducing individual catchment loads to specific levels.

“Previous research using in situ observations, remote-sensing and modelling has shown the broad negative impact of catchment loads on GBR water quality. eReefs modelling has allowed us to delve deeper,” said Dr Baird.

“Determining the impact that proposed changes in agricultural management actions have on marine water quality requires two models. One model to simulate the impact of management actions on catchment loads and a marine model to simulate the water quality response to these changes in catchment loads.”

“Coupling the Queensland Government Dynamic SedNet catchment model to the eReefs hydrodynamic-biogeochemical model, we have been able to simulate the whole system. In doing so, we’ve been able to determine how much we need to reduce pollutant loads to achieve the water quality improvements that will deliver positive ecological outcomes for the reef.”

The team analysed water quality responses to specific catchment load scenarios over the time period 2011 to 2018. The techniques they used allowed them to separately estimate the impact of natural and anthropogenic (human-derived) portions of catchment loads. The eReefs simulations confirmed that reducing anthropogenic pollutant loads results in improved water quality, especially within river plumes. This provides confidence that the actions being undertaken on-farm and in catchments to reduce nutrient and sediment loads are worthwhile and that future GBR water quality will benefit from continued improvements in catchment management.

Model output from the coupled eReefs marine model on the day of the satellite image above, showing: surface salinity, surface percentage of Burdekin river water , surface suspended sediment and simulated true colour, calculated from the absorption and scattering properties of over 20 modelled optically active constituents at the red, green and blue wavelengths. Thus, the brown of the river plume of the Burdekin and Haughton is due to the spatial-resolved model concentration of suspended sediment and the colour of sediment particles in the Burdekin plume and compares favourably with the polar-orbiting satellite image of Figure 1.

The team’s research has underpinned the water quality improvement and pollutant load reduction targets set as part of the Reef 2050 Water Quality Improvement Plan 2017-2022. Their work has helped to develop targets that are neither too high nor too low. Ensuring they will achieve the necessary water quality improvements without requiring any unnecessary actions to be taken.

Along with informing water quality improvement targets, eReefs has been used in reporting on the environmental condition of and outlook for the GBR, evaluating the occurrence and spread of crown-of-thorns starfish outbreaks, assessing coral bleaching and ocean acidification vulnerability at the whole-of-GBR scale, and forecasting the potential impacts of floods, cyclones and elevated sea surface temperatures on the GBR. By providing science-backed information about the environmental factors impacting the reef on which managers of the GBR have based their decisions, eReefs has delivered significant economic, social and environmental returns for Australia.

Globally, there is growing concern about the long-term viability of coral reefs. The complexity of these ecosystems and the significant threats they face make the task of managing them no mean feat. However, the success of eReefs shows how information can be used to aid decision-making for informed coral reef management, which will hopefully turn the tide and ensure these unique ecosystems are around for a long time to come.

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